The present invention relates to semiconductor manufacturing. More specifically, the present invention relates to a method of making bonded sapphire structures wherein the mating surfaces are aligned along like lattice planes.
Sapphire is increasingly becoming the material of choice for engineers faced with the design challenges of extreme conditions, such as those found in high-temperature, high-pressure or harsh chemical environments. Its unique properties make it a cost-effective solution for those applications where long life and high performance are a must.
One of the hardest materials in existence, sapphire is virtually scratch proof. It has a melting point of over 2000 degrees C., making it ideal for high temperature applications. It is chemically inert and easily withstands harsh chemicals such as fluorine plasma (used extensively in the semiconductor industry) and other industrial gases and fluids, with no particle generation. In addition, sapphire can transmit ultraviolet, visible and infrared light, as well as microwaves, a range broader than most materials. Sapphire has been used in such diverse applications as providing shielding for the nose cones of a missiles which can transmit laser light information therethrough, or providing guide tubes, protective shields, or support structures for various processes used in the manufacturing of semiconductor devices.
Single crystal sapphire is usually grown in boules or ingots. Boules are generally pear shaped or cylindrical masses formed synthetically in a special furnace with the atomic structure of a single crystal. These boules can be sliced or machined to fit the shape of the required structure needed.
However, it is very difficult to grow sapphire boules that are larger than 2 to 3 inches in diameter. Additionally, the machining operations on the boules can be expensive. Therefore, prior art methods of producing large sapphire structures having overall dimensions in excess of these diameters are very difficult and expensive to make. Examples of such sapphire structures would be large hollow domes, polygons or spherical structures used as shielding in the semiconductor or military industries.
Additionally, prior art sapphire structures used in the production of silicon wafers must also be able to withstand high temperature processing of the wafers without damage. However, expansion and contraction during these high temperature operations will often cause trouble with bonding materials used to construct prior art sapphire structures. Even different prior art structural components composed entirely of single crystal sapphire will encounter problems with different coefficients of expansion along the different lattice planes of the crystal.
Based on the foregoing, it is the general object of the present invention to provide a method of making a sapphire structure that overcomes the problems and drawbacks associated with prior art contamination control structures.
The present invention offers advantages and alternatives over the prior art by providing in a first aspect a method for making a single crystal structure. The method including selecting a plurality of single crystal components having a lattice unit cell repeated substantially throughout, the unit cell having a periodic arrangement of atoms defining a set of lattice planes. Determining the orientations of the lattice planes relative to each component. Machining each component along at least one of the set of lattice planes to define a pair of interface surfaces thereon. Applying bonding material to each interface surface. Assembling the components at their respective interface surfaces such that each pair of matching interface surfaces have an orientation substantially aligned along a common one of the set of lattice planes. Heating the components per a predetermined temperature profile until the bonding material melts and fuses the components together.
In an alternative embodiment of the invention the method includes selecting a plurality of sapphire components. Additionally, the components can be either panels and/or structural members.
In another alternative embodiment the method includes applying a eutectic bonding material to the components.